How To Read A Window Label

How to read a window label

So, you have decided to replace your windows.

You have already picked out the materials and style that you want.

You arrive at the dealer (which, hopefully, is your local Windowrama showroom).

But once you begin browsing, you suddenly find yourself struggling to read the labels.

That’s normal: When it finally comes time to select your new windows, you may encounter some unfamiliar phrases in the product descriptions. It’s only industry jargon. However, understanding it will make it easier for you to select the right window.

Below are a few terms to know before you choose your product:


  • Measures how well a product can keep heat from escaping from the inside of a room. The lower the number, the better a product is at keeping heat in.
  • Range:20-1.20
  • Look for: Low numbers

Solar Heat Gain Coefficient

  • Measures how well a product can resist unwanted heat gain, which is especially important during the summer cooling season. The lower the number, the less you’ll spend on cooling.
  • Range: 0-1
  • Look for: Low numbers

Visible Transmittance

  • Measures how well a product is designed to effectively illuminate your home with daylight, potentially saving you money on artificial lighting. The higher the number, the more natural light is let in.
  • Range: 0–1
  • Look for: High numbers

Air Leakage

  • Measures how much air will enter a room through a product. The lower the number, the fewer drafts you’ll experience.
  • Range:1-0.3
  • Look for: Low numbers

To learn more, download your free Window Replacement 101 guide.

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